Exhaust purification device for internal combustion engine

摘要

In order to prevent a decrease in the accuracy with which filter malfunctions are determined due to a decrease in the detection accuracy of a PM sensor, the present invention is equipped with a filter, a selective reduction NOx catalyst provided downstream from the filter, a PM sensor that is downstream from the selective reduction NOx catalyst, and that detects the amount of particulate matter, and a removal unit that executes a process to remove the reduction agent adhering to the PM sensor in at least one of these situations: when the temperature of the selective reduction NOx catalyst is equal to or less than a threshold value; when the exhaust temperature is equal to or less than a threshold value; when the flow volume of the exhaust is equal to or greater than a threshold value; when the adsorption amount of the reduction agent in the selective reduction NOx catalyst is equal to or greater than a threshold value.